Too many rounds wasted to get to the target.
German Army infantry tactics centered around the LMG. The MG was viewed as a long range shotgun that delivered a helluva lot of 7.92 rounds into a LOOOONG eliptically shaped beaten zone, enabling the MG crews squad mates (who acted as ammo bearers) to manuever and overrun the enemy on the offensive or for them to protect the MG crew’s blindspots on the defenseive.
The extent to which the Germans believed in this idea is reflected in the fact that the MG 42’s cyclic rate was 1200 rpm as opposed to the MG 34’s 850 or so.
MG 42 had the best and quickest barrel change in the business. It had to, given that high rate of fire.